signature DOT_STRUCTS =
sig
end

signature DOT =
sig
  include DOT_STRUCTS
  
  structure Content :
  sig
    datatype t 
      = T of {head : string,
              tail : string} list
    
    val toString : t -> string
  end
  
  datatype t
    = T of {name : string,
            size : {width : int, height : int},
            node : {color : string, style : string},
            contents : Content.t}
  
  val outputFile : t -> unit
end